Four steps of gcc

Posted 2022-12-09 sununs11

Four steps of gcc: preprocessing, compilation, assembly and linking.

hello.c

----------------------------------------------------------------------------------

#include <stdio.h>

int main()

printf("hello world!/n");

return 0;

----------------------------------------------------------------------------------

hello.c

First,preprocessing.

Input:

gcc -E hello.c -o hello.i

Then I got a file called "hello.i".

-----------------------------------------------------------------------------------

# 1 "hello.c"

# 1 "<built-in>"

# 1 "<command-line>"

# 1 "hello.c"

# 1 "/usr/include/stdio.h" 1 3 4

# 28 "/usr/include/stdio.h" 3 4

# 1 "/usr/include/features.h" 1 3 4

# 322 "/usr/include/features.h" 3 4

# 1 "/usr/include/bits/predefs.h" 1 3 4

# 323 "/usr/include/features.h" 2 3 4

# 355 "/usr/include/features.h" 3 4

# 1 "/usr/include/sys/cdefs.h" 1 3 4

# 353 "/usr/include/sys/cdefs.h" 3 4

# 1 "/usr/include/bits/wordsize.h" 1 3 4

# 354 "/usr/include/sys/cdefs.h" 2 3 4

# 356 "/usr/include/features.h" 2 3 4

# 387 "/usr/include/features.h" 3 4

# 1 "/usr/include/gnu/stubs.h" 1 3 4

# 1 "/usr/include/bits/wordsize.h" 1 3 4

# 5 "/usr/include/gnu/stubs.h" 2 3 4

# 1 "/usr/include/gnu/stubs-32.h" 1 3 4

# 8 "/usr/include/gnu/stubs.h" 2 3 4

# 388 "/usr/include/features.h" 2 3 4

# 29 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stddef.h" 1 3 4

# 211 "/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stddef.h" 3 4

typedef unsigned int size_t;

# 35 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/include/bits/types.h" 1 3 4

# 28 "/usr/include/bits/types.h" 3 4

# 1 "/usr/include/bits/wordsize.h" 1 3 4

# 29 "/usr/include/bits/types.h" 2 3 4

typedef unsigned char __u_char;

typedef unsigned short int __u_short;

typedef unsigned int __u_int;

typedef unsigned long int __u_long;

typedef signed char __int8_t;

typedef unsigned char __uint8_t;

typedef signed short int __int16_t;

typedef unsigned short int __uint16_t;

typedef signed int __int32_t;

typedef unsigned int __uint32_t;

__extension__ typedef signed long long int __int64_t;

__extension__ typedef unsigned long long int __uint64_t;

__extension__ typedef long long int __quad_t;

__extension__ typedef unsigned long long int __u_quad_t;

# 131 "/usr/include/bits/types.h" 3 4

# 1 "/usr/include/bits/typesizes.h" 1 3 4

# 132 "/usr/include/bits/types.h" 2 3 4

__extension__ typedef __u_quad_t __dev_t;

__extension__ typedef unsigned int __uid_t;

__extension__ typedef unsigned int __gid_t;

__extension__ typedef unsigned long int __ino_t;

__extension__ typedef __u_quad_t __ino64_t;

__extension__ typedef unsigned int __mode_t;

__extension__ typedef unsigned int __nlink_t;

__extension__ typedef long int __off_t;

__extension__ typedef __quad_t __off64_t;

__extension__ typedef int __pid_t;

__extension__ typedef struct int __val[2]; __fsid_t;

__extension__ typedef long int __clock_t;

__extension__ typedef unsigned long int __rlim_t;

__extension__ typedef __u_quad_t __rlim64_t;

__extension__ typedef unsigned int __id_t;

__extension__ typedef long int __time_t;

__extension__ typedef unsigned int __useconds_t;

__extension__ typedef long int __suseconds_t;

__extension__ typedef int __daddr_t;

__extension__ typedef long int __swblk_t;

__extension__ typedef int __key_t;

__extension__ typedef int __clockid_t;

__extension__ typedef void * __timer_t;

__extension__ typedef long int __blksize_t;

__extension__ typedef long int __blkcnt_t;

__extension__ typedef __quad_t __blkcnt64_t;

__extension__ typedef unsigned long int __fsblkcnt_t;

__extension__ typedef __u_quad_t __fsblkcnt64_t;

__extension__ typedef unsigned long int __fsfilcnt_t;

__extension__ typedef __u_quad_t __fsfilcnt64_t;

__extension__ typedef int __ssize_t;

typedef __off64_t __loff_t;

typedef __quad_t *__qaddr_t;

typedef char *__caddr_t;

__extension__ typedef int __intptr_t;

__extension__ typedef unsigned int __socklen_t;

# 37 "/usr/include/stdio.h" 2 3 4

# 45 "/usr/include/stdio.h" 3 4

struct _IO_FILE;

typedef struct _IO_FILE FILE;

# 65 "/usr/include/stdio.h" 3 4

typedef struct _IO_FILE __FILE;

# 75 "/usr/include/stdio.h" 3 4

# 1 "/usr/include/libio.h" 1 3 4

# 32 "/usr/include/libio.h" 3 4

# 1 "/usr/include/_G_config.h" 1 3 4

# 15 "/usr/include/_G_config.h" 3 4

# 1 "/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stddef.h" 1 3 4

# 16 "/usr/include/_G_config.h" 2 3 4

# 1 "/usr/include/wchar.h" 1 3 4

# 83 "/usr/include/wchar.h" 3 4

typedef struct

int __count;

union

unsigned int __wch;

char __wchb[4];

__value;

__mbstate_t;

# 21 "/usr/include/_G_config.h" 2 3 4

typedef struct

__off_t __pos;

__mbstate_t __state;

_G_fpos_t;

typedef struct

__off64_t __pos;

__mbstate_t __state;

_G_fpos64_t;

# 53 "/usr/include/_G_config.h" 3 4

typedef int _G_int16_t __attribute__ ((__mode__ (__HI__)));

typedef int _G_int32_t __attribute__ ((__mode__ (__SI__)));

typedef unsigned int _G_uint16_t __attribute__ ((__mode__ (__HI__)));

typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__)));

# 33 "/usr/include/libio.h" 2 3 4

# 53 "/usr/include/libio.h" 3 4

# 1 "/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stdarg.h" 1 3 4

# 40 "/usr/lib/gcc/i686-linux-gnu/4.4.5/include/stdarg.h" 3 4

typedef __builtin_va_list __gnuc_va_list;

# 54 "/usr/include/libio.h" 2 3 4

# 170 "/usr/include/libio.h" 3 4

struct _IO_jump_t; struct _IO_FILE;

# 180 "/usr/include/libio.h" 3 4

typedef void _IO_lock_t;

struct _IO_marker

struct _IO_marker *_next;

struct _IO_FILE *_sbuf;

int _pos;

# 203 "/usr/include/libio.h" 3 4

;

enum __codecvt_result

__codecvt_ok,

__codecvt_partial,

__codecvt_error,

__codecvt_noconv

;

# 271 "/usr/include/libio.h" 3 4

struct _IO_FILE

int _flags;

char* _IO_read_ptr;

char* _IO_read_end;

char* _IO_read_base;

char* _IO_write_base;

char* _IO_write_ptr;

char* _IO_write_end;

char* _IO_buf_base;

char* _IO_buf_end;

char *_IO_save_base;

char *_IO_backup_base;

char *_IO_save_end;

struct _IO_marker *_markers;

struct _IO_FILE *_chain;

int _fileno;

int _flags2;

__off_t _old_offset;

unsigned short _cur_column;

signed char _vtable_offset;

char _shortbuf[1];

_IO_lock_t *_lock;

# 319 "/usr/include/libio.h" 3 4

__off64_t _offset;

# 328 "/usr/include/libio.h" 3 4

void *__pad1;

void *__pad2;

void *__pad3;

void *__pad4;

size_t __pad5;

int _mode;

char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)];

;

typedef struct _IO_FILE _IO_FILE;

struct _IO_FILE_plus;

extern struct _IO_FILE_plus _IO_2_1_stdin_;

extern struct _IO_FILE_plus _IO_2_1_stdout_;

extern struct _IO_FILE_plus _IO_2_1_stderr_;

# 364 "/usr/include/libio.h" 3 4

typedef __ssize_t __io_read_fn (void *__cookie, char *__buf, size_t __nbytes);

typedef __ssize_t __io_write_fn (void *__cookie, __const char *__buf,

size_t __n);

typedef int __io_seek_fn (void *__cookie, __off64_t *__pos, int __w);

typedef int __io_close_fn (void *__cookie);

# 416 "/usr/include/libio.h" 3 4

extern int __underflow (_IO_FILE *);

extern int __uflow (_IO_FILE *);

extern int __overflow (_IO_FILE *, int);

# 460 "/usr/include/libio.h" 3 4

extern int _IO_getc (_IO_FILE *__fp);

extern int _IO_putc (int __c, _IO_FILE *__fp);

extern int _IO_feof (_IO_FILE *__fp) __attribute__ ((__nothrow__));

extern int _IO_ferror (_IO_FILE *__fp) __attribute__ ((__nothrow__));

extern int _IO_peekc_locked (_IO_FILE *__fp);

extern void _IO_flockfile (_IO_FILE *) __attribute__ ((__nothrow__));

extern void _IO_funlockfile (_IO_FILE *) __attribute__ ((__nothrow__));

extern int _IO_ftrylockfile (_IO_FILE *) __attribute__ ((__nothrow__));

# 490 "/usr/include/libio.h" 3 4

extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict,

__gnuc_va_list, int *__restrict);

extern int _IO_vfprintf (_IO_FILE *__restrict, const char *__restrict,

__gnuc_va_list);

extern __ssize_t _IO_padn (_IO_FILE *, int, __ssize_t);

extern size_t _IO_sgetn (_IO_FILE *, void *, size_t);

extern __off64_t _IO_seekoff (_IO_FILE *, __off64_t, int, int);

extern __off64_t _IO_seekpos (_IO_FILE *, __off64_t, int);

extern void _IO_free_backup_area (_IO_FILE *) __attribute__ ((__nothrow__));

# 76 "/usr/include/stdio.h" 2 3 4

typedef __gnuc_va_list va_list;

# 91 "/usr/include/stdio.h" 3 4

typedef __off_t off_t;

# 103 "/usr/include/stdio.h" 3 4

typedef __ssize_t ssize_t;

typedef _G_fpos_t fpos_t;

# 161 "/usr/include/stdio.h" 3 4

# 1 "/usr/include/bits/stdio_lim.h" 1 3 4

# 162 "/usr/include/stdio.h" 2 3 4

extern struct _IO_FILE *stdin;

extern struct _IO_FILE *stdout;

extern struct _IO_FILE *stderr;

extern int remove (__const char *__filename) __attribute__ ((__nothrow__));

extern int rename (__const char *__old, __const char *__new) __attribute__ ((__nothrow__));

extern int renameat (int __oldfd, __const char *__old, int __newfd,

__const char *__new) __attribute__ ((__nothrow__));

extern FILE *tmpfile (void) ;

# 206 "/usr/include/stdio.h" 3 4

extern char *tmpnam (char *__s) __attribute__ ((__nothrow__)) ;

extern char *tmpnam_r (char *__s) __attribute__ ((__nothrow__)) ;

# 224 "/usr/include/stdio.h" 3 4

extern char *tempnam (__const char *__dir, __const char *__pfx)

__attribute__ ((__nothrow__)) __attribute__ ((__malloc__)) ;

extern int fclose (FILE *__stream);

extern int fflush (FILE *__stream);

# 249 "/usr/include/stdio.h" 3 4

extern int fflush_unlocked (FILE *__stream);

# 263 "/usr/include/stdio.h" 3 4

extern FILE *fopen (__const char *__restrict __filename,

__const char *__restrict __modes) ;

extern FILE *freopen (__const char *__restrict __filename,

__const char *__restrict __modes,

FILE *__restrict __stream) ;

# 292 "/usr/include/stdio.h" 3 4

# 303 "/usr/include/stdio.h" 3 4

extern FILE *fdopen (int __fd, __const char *__modes) __attribute__ ((__nothrow__)) ;

# 316 "/usr/include/stdio.h" 3 4

extern FILE *fmemopen (void *__s, size_t __len, __const char *__modes)

__attribute__ ((__nothrow__)) ;

extern FILE *open_memstream (char **__bufloc, size_t *__sizeloc) __attribute__ ((__nothrow__)) ;

extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __attribute__ ((__nothrow__));

extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf,

int __modes, size_t __n) __attribute__ ((__nothrow__));

extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf,

size_t __size) __attribute__ ((__nothrow__));

extern void setlinebuf (FILE *__stream) __attribute__ ((__nothrow__));

extern int fprintf (FILE *__restrict __stream,

__const char *__restrict __format, ...);

extern int printf (__const char *__restrict __format, ...);

extern int sprintf (char *__restrict __s,

__const char *__restrict __format, ...) __attribute__ ((__nothrow__));

extern int vfprintf (FILE *__restrict __s, __const char *__restrict __format,

__gnuc_va_list __arg);

extern int vprintf (__const char *__restrict __format, __gnuc_va_list __arg);

extern int vsprintf (char *__restrict __s, __const char *__restrict __format,

__gnuc_va_list __arg) __attribute__ ((__nothrow__));

extern int snprintf (char *__restrict __s, size_t __maxlen,

__const char *__restrict __format, ...)

__attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 4)));

extern int vsnprintf (char *__restrict __s, size_t __maxlen,

__const char *__restrict __format, __gnuc_va_list __arg)

__attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 0)));

# 414 "/usr/include/stdio.h" 3 4

extern int vdprintf (int __fd, __const char *__restrict __fmt,

__gnuc_va_list __arg)

__attribute__ ((__format__ (__printf__, 2, 0)));

extern int dprintf (int __fd, __const char *__restrict __fmt, ...)

__attribute__ ((__format__ (__printf__, 2, 3)));

extern int fscanf (FILE *__restrict __stream,

__const char *__restrict __format, ...) ;

extern int scanf (__const char *__restrict __format, ...) ;

extern int sscanf (__const char *__restrict __s,

__const char *__restrict __format, ...) __attribute__ ((__nothrow__));

# 445 "/usr/include/stdio.h" 3 4

extern int fscanf (FILE *__restrict __stream, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf") ;

extern int scanf (__const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf") ;

extern int sscanf (__const char *__restrict __s, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__));

# 465 "/usr/include/stdio.h" 3 4

extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format,

__gnuc_va_list __arg)

__attribute__ ((__format__ (__scanf__, 2, 0))) ;

extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg)

__attribute__ ((__format__ (__scanf__, 1, 0))) ;

extern int vsscanf (__const char *__restrict __s,

__const char *__restrict __format, __gnuc_va_list __arg)

__attribute__ ((__nothrow__)) __attribute__ ((__format__ (__scanf__, 2, 0)));

# 496 "/usr/include/stdio.h" 3 4

extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf")

__attribute__ ((__format__ (__scanf__, 2, 0))) ;

extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf")

__attribute__ ((__format__ (__scanf__, 1, 0))) ;

extern int vsscanf (__const char *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__))

__attribute__ ((__format__ (__scanf__, 2, 0)));

# 524 "/usr/include/stdio.h" 3 4

extern int fgetc (FILE *__stream);

extern int getc (FILE *__stream);

extern int getchar (void);

# 552 "/usr/include/stdio.h" 3 4

extern int getc_unlocked (FILE *__stream);

extern int getchar_unlocked (void);

# 563 "/usr/include/stdio.h" 3 4

extern int fgetc_unlocked (FILE *__stream);

extern int fputc (int __c, FILE *__stream);

extern int putc (int __c, FILE *__stream);

extern int putchar (int __c);

# 596 "/usr/include/stdio.h" 3 4

extern int fputc_unlocked (int __c, FILE *__stream);

extern int putc_unlocked (int __c, FILE *__stream);

extern int putchar_unlocked (int __c);

extern int getw (FILE *__stream);

extern int putw (int __w, FILE *__stream);

extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream)

;

extern char *gets (char *__s) ;

# 658 "/usr/include/stdio.h" 3 4

extern __ssize_t __getdelim (char **__restrict __lineptr,

size_t *__restrict __n, int __delimiter,

FILE *__restrict __stream) ;

extern __ssize_t getdelim (char **__restrict __lineptr,

size_t *__restrict __n, int __delimiter,

FILE *__restrict __stream) ;

extern __ssize_t getline (char **__restrict __lineptr,

size_t *__restrict __n,

FILE *__restrict __stream) ;

extern int fputs (__const char *__restrict __s, FILE *__restrict __stream);

extern int puts (__const char *__s);

extern int ungetc (int __c, FILE *__stream);

extern size_t fread (void *__restrict __ptr, size_t __size,

size_t __n, FILE *__restrict __stream) ;

extern size_t fwrite (__const void *__restrict __ptr, size_t __size,

size_t __n, FILE *__restrict __s);

# 730 "/usr/include/stdio.h" 3 4

extern size_t fread_unlocked (void *__restrict __ptr, size_t __size,

size_t __n, FILE *__restrict __stream) ;

extern size_t fwrite_unlocked (__const void *__restrict __ptr, size_t __size,

size_t __n, FILE *__restrict __stream);

extern int fseek (FILE *__stream, long int __off, int __whence);

extern long int ftell (FILE *__stream) ;

extern void rewind (FILE *__stream);

# 766 "/usr/include/stdio.h" 3 4

extern int fseeko (FILE *__stream, __off_t __off, int __whence);

extern __off_t ftello (FILE *__stream) ;

# 785 "/usr/include/stdio.h" 3 4

extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos);

extern int fsetpos (FILE *__stream, __const fpos_t *__pos);

# 808 "/usr/include/stdio.h" 3 4

# 817 "/usr/include/stdio.h" 3 4

extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__));

extern int feof (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern int ferror (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__));

extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern void perror (__const char *__s);

# 1 "/usr/include/bits/sys_errlist.h" 1 3 4

# 27 "/usr/include/bits/sys_errlist.h" 3 4

extern int sys_nerr;

extern __const char *__const sys_errlist[];

# 847 "/usr/include/stdio.h" 2 3 4

extern int fileno (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__)) ;

# 866 "/usr/include/stdio.h" 3 4

extern FILE *popen (__const char *__command, __const char *__modes) ;

extern int pclose (FILE *__stream);

extern char *ctermid (char *__s) __attribute__ ((__nothrow__));

# 906 "/usr/include/stdio.h" 3 4

extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__));

extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__)) ;

extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__));

# 936 "/usr/include/stdio.h" 3 4

# 2 "hello.c" 2

int main()

printf("hello world!");

return 0;

----------------------------------------------------------------------------------

hello.i

That's so complex!

And then,compilation.

Input:

gcc -S hello.i -o hello.s

I got a "hello.s".

hello.s

-----------------------------------------------------------------------

.file"hello.c"

.section.rodata

.LC0:

.string"hello world!"

.text

.globl main

.typemain, @function

main:

pushl%ebp

movl%esp, %ebp

andl$-16, %esp

subl$16, %esp

movl$.LC0, %eax

movl%eax, (%esp)

callprintf

movl$0, %eax

leave

ret

.sizemain, .-main

.ident"GCC: (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5"

.section.note.GNU-stack,"",@progbits

----------------------------------------------------------------------------

hello.s

Hmm,That's pretty good!I can understand some of it.

The third step,assembly.

Input:

gcc -c hello.s -o hello.o

It is a binary code file,We can't read it in a normal way.

The last step,linking.

Input:

gcc hello.o -o hello

./hello

Output:

hello world!